Halogenopyridines pyridynes from

While awaiting the results of tracer experiments, the present authors prefer to desist from assuming that the route from 24 to 25 via the addition product shown is the only pathway followed in the amination of 2-halogenopyridines. This is the more so since it seems probable that in the experiments described below derivatives of 2,3-pyridyne occur as intermediates. 

Pyridynes are also commonly generated from orf/io-dihalogenopyridines by lithium exchange processes, e.g. Scheme 138, and processes not involving halogenopyridines, e.g. thermal decomposition of pyridinediazonium carboxylates. 

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